1. Field of the Invention
The present invention relates to a photopolymerizable composition and a recording material which are both novel. More specifically, the invention relates to such a photopolymerizable composition and a recording material favorable for use in, for example, inks, color filters, holograms, proofs, sealants, adhesives, lithographic prints, resin relief prints, and photoresists.
2. Description of the Related Art
A photopolymerizable composition basically comprises a photopolymerization initiator and an addition-polymerizable compound containing at least 2 ethylenic unsaturated bonds in one molecule (this is hereinafter referred to as a xe2x80x9cpolyfunctional monomerxe2x80x9d). The photopolymerizable composition hardens, when exposed to light, and its cohesiveness changes and it thus becomes insoluble in solvents. In order to take advantage of these properties, the composition is widely utilized in, for example, photographs, prints, metal surface processing techniques and inks. The functions and the applications of such a photopolymerizable compositions are described in various publications.
They are described in detail, for example, in J. Kosar""s Light Sensitive Systems (J. Wiley and Sons, New York, 1965, pp. 158-193); and K. I. Jacobson and R. E. Jacobson""s Imaging Systems (J. Wiley and Sons, New York, 1976, pp. 181-222).
In recent years, an image formation system utilizing photosensitive microcapsule in which a photopolymerizable composition is contained has been proposed. For example, JP-A 57-124343, 57-179836 and 57-197538 disclose a method of forming color images, which comprises exposing a color-forming sheet (which is coated with microcapsules that contain a photopolymerizable composition comprising a vinyl compound and a photopolymerization initiator, and a dye) to light, then superposing an image-receiving sheet onto it, and applying pressure to thereby form a color image on the image-receiving sheet.
JP-A 3-87827 and 4-211252 disclose a photosensitive thermal recording material for color image formation thereon, which contains two components and in which one of the two components is encapsulated in microcapsules and the other is a curable compound of a photocurable composition. The second component may also be outside the microcapsules along with a photocurable composition. One example of the photosensitive thermal recording material disclosed in the latter has a layer that contains microcapsules of an electron-donating leuco-dye, and contains, outside the microcapsules, a photocurable composition that comprises an electron-receiving compound, a polymerizable vinyl monomer and a photopolymerization initiator.
As mentioned above, the recording material comprising a photopolymerizable composition can be processed for image formation thereon in a complete dry system not requiring developer and thus not producing waste, and is therefore very favorable in view of protection of the environment.
In image formation on such photosensitive recording materials, using not only UV rays and short-wave visible rays but also inexpensive IR lasers and blue to red rays, if possible, is desired. However, most recording materials that comprise a conventional photopolymerizable composition are sensitive to UV rays but not to rays in the visible to IR range, and even if they are sensitive also to rays in the visible to IR range, their sensitivity is insufficient. As a result, the images formed on them are often blurred, and the contrast between the image area and the non-image area therein is often low. Therefore, it is desired to further increase the sensitivity of conventional recording materials.
In general, spectral sensitizing dyes are used in these recording materials for enhancing the sensitivity of the materials to light to which they are exposed for image recording (writing) thereon. However, after images have been recorded on them through exposure to light, the materials are again exposed to light which the dyes therein can absorb and by which the dyes are photodecomposed so that their colors are completely erased from the image-recorded materials. Namely, the recording materials containing such spectral sensitizing dyes are required to have the ability to erase the colors of the dyes in order that sharp and high-contrast images can be formed on them.
The present invention is to solve the prior-art problems mentioned above, and to attain the objects mentioned below.
Specifically, one object of the invention is to provide a photopolymerizable composition highly sensitive to not only UV rays but also rays in the visible to IR range.
Another object of the invention is to provide a recording material which is capable of highly sensitive image recording using not only UV rays but also rays in the visible to IR range and which is processable in a completely-dry system which does not require developer and does not produce waste, and in which the colors in its non-image area (background area) can be erased and on which sharp and high-contrast black-and-white or color images can be formed.
The means of the invention for solving the problems mentioned above are as follows.
The invention provides a photopolymerizable composition that comprises a polymerizable compound having an ethylenic unsaturated bond, a compound of the following general formula (1), and a radical generator capable of interacting with the compound of formula (1) to generate a radical: 
wherein R1 and R2 each independently represents an aliphatic group or an aromatic group; R3 represents a group of the following formula: 
R4 represents an aliphatic group or an aromatic group; R5 represents a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group; L1, L2, L3 and L4 each independently represents a substituted or unsaturated methine group, and in the case where L1, L2, L3 and L4 each represents a methine group having a substituent, the substituents may be bonded to each other to form an unsaturated aliphatic ring or an unsaturated hetero ring; Z1, Z2 and Z3 each independently represents an atomic group which forms a 5-membered nitrogen-containing hetero ring, and the nitrogen-containing hetero ring may be condensed with any of an aromatic ring or a hetero ring, and the nitrogenxe2x80x94containing hetero ring as well as the aromatic ring and the hetero ring, if condensed with the nitrogen-containing hetero ring, may be substituted or unsubstituted; and Xxe2x88x92 represents a group which forms an anion.
In one embodiment of the photopolymerizable composition of the invention, the compound of formula (1) is any one of a compound of the following general formula (2) and a compound of the following general formula (3): 
wherein R21, R22 and R23 each independently represents an aliphatic group or an aromatic group; R24 represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group; L21, L22, L23 and L24 each independently represents a substituted or unsubstituted methine group; Y21, Y22 and Y23 each independently represents xe2x80x94CR25R26xe2x80x94, xe2x80x94NR27xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Sexe2x80x94 or xe2x80x94Texe2x80x94; R25, R26 and R27 each independently represents a hydrogen atom, an aliphatic group or an aromatic group; R25 and R26 may be atomic groups bonded to each other to form a ring; the benzene rings Z21, Z22 and Z23 may be condensed with other benzene rings; the benzene rings Z21, Z22 and Z23 as well as the other benzene rings, if any, which are condensed with the benzene rings Z21, Z22 and Z23 maybe substituted or unsubstituted; and Xxe2x88x92 represents an anion.
In another embodiment of the invention, the photopolymerizable composition comprises a polymerizable compound having an ethylenic unsaturated bond, a compound of the following general formula (4), and a radical generator capable of interacting with the compound of formula (4) to generate a radical: 
wherein R11 and R12 each independently represents an aliphatic group or an aromatic group; R13 represents a group of the following formula: 
R4 represents an aliphatic group or an aromatic group; R5 represents a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group; L11, L12, L13, L14, L3 and L4 each independently represents an substituted or unsubstituted methine group, and in the case where L11, L12, L13, L14, L3 and L4 each represents a methine group having a subsituent, the substituent may be bonded to each other to form an unsaturated aliphatic ring or an unsaturated hetero ring; Z11, Z12 and Z3 each independently represents an atomic group which forms a 5-membered nitrogen-containing hetero ring, the nitrogen-containing hetero ring may be condensed with any of an aromatic ring or a hetero ring, and the nitrogen-containing hetero ring as well as the aromatic ring and the hetero ring, if condensed with the nitrogen-containing hetero ring, may be substituted or unsubstituted; n indicates 0, 1 or 2; and Xxe2x88x92 represents a group which forms an anion.
In still another embodiment of the photopolymerizable composition of the invention, the compound of formula (4) is any one of a compound of the following general formula (5) and a compound of the following general formula (6): 
wherein R31, R32 and R33 each independently represents an aliphatic group or an aromatic group; R34 represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group; L31, L32, L33, L34, L35 and L36 each independently represents an substituted or unsubstituted methine group; Y31, Y32 and Y33 each independently represents xe2x80x94CR35R36xe2x80x94, xe2x80x94NR37xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Sexe2x80x94 or xe2x80x94Texe2x80x94; R35, R36 and R37 each independently represents a hydrogen atom, an aliphatic group or an aromatic group; R35 and R36 may be atomic groups bonded to each other to form a ring; the benzene rings Z31, Z32 and Z33 may be condensed with other benzene rings; the benzene rings Z31, Z32 and Z33 as well as the other benzene rings, if any, which are condensed with the benzene rings Z31, Z32 and Z33 may be substituted or unsubstituted; and Xxe2x88x92 represents an anion.
In still another embodiment of the photopolymerizable composition of the invention, the radical generator is an organoboron compound.
In still another embodiment of the photopolymerizable composition of the invention, the organoboron compound is represented by the following general formula (A): 
wherein Ra1, Ra2, Ra3 and Ra4 each independently represents an aliphatic group, an aromatic group, a heterocyclic group, or Si (Ra5) (Ra6) xe2x80x94Ra7; Ra5, Ra6 and Ra7 each independently represents an aliphatic group or an aromatic group; and G+ represents a group to form a cation.
The invention also provides a recording material having a recording layer on a support, in which the recording layer contains at least a color-forming component A, a color-forming component B having a site that reacts with the color-forming component A to form a color, and the above-mentioned photopolymerizable composition.
In one embodiment of the recording material of the invention, at least one of the polymerizable compounds having an ethylenic unsaturated bond is the color-forming component B.
In still another embodiment of the recording material of the invention, the polymerizable compound having an ethylenic unsaturated bond is a color formation-inhibiting compound which additionally has, in one molecule, a site that inhibits the reaction of the color-forming components A and B.
In still another embodiment of the recording material of the invention, the color-forming component A is in microcapsules.
In still another embodiment of the recording material of the invention, the radical generator is an organoboron compound.